Spermophilus beecheyi was named for Frederick William Beechey, who spent time exploring Northern California from 1826-1828. This species used to be known as Otospermophilus beecheyi.
California ground squirrels use a variety of sounds, tail signals and scent production as means of communication. For example, glandular folds anterior to the tail region are used for individual identification. When finding a mate or mates, females may approach or males may approach, but scent cues are important in identifying reproductive condition.
Communication Channels: visual ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
There are no special conservation practices currently for S. beecheyi. Some control of their numbers has been attempted, costing several hundred thousand dollars. These are generally targeted responses to crop damage or disease outbreaks.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
This species may threaten agricultural crops, such as grain fields and orchards, through their foraging activities. They are potential carriers of diseases, such as tularemia, bubonic plague, and sylvatic plague. The two latter diseases are from fleas the squirrels carry.
Negative Impacts: injures humans (carries human disease); crop pest; causes or carries domestic animal disease
Due to their diet, California ground squirrels could play a role in regulating some insect populations. They may aid in seed dispersal when a cache is forgotten. they help to aerate the soil through their excavation of burrows, and create habitat for many other animals, such as other rodents and snakes, which occupy empty burrows.
Ecosystem Impact: disperses seeds; creates habitat; soil aeration
California ground squirrels use cheek pouches while they are foraging to collect more food than would otherwise be possible in one sitting. They are also known to cache or store food. They exploit a variety of food sources, which probably contributes to their success as a species.
The diet of these animals, as their genus name would suggest, is primarily seed-based. California ground squirrels consume seeds, barley, oats, and acorns (Quercus): valley oak, blue oak, coast oak). They also eat fruits, like gooseberries and pears, and quail (Callipepla) eggs. They include insects in their diets when they are available, and have been known to eat grasshoppers, crickets, beetles and caterpillars. They also eat roots, bulbs, and fungi, such as mushrooms.
Animal Foods: eggs; insects
Plant Foods: roots and tubers; seeds, grains, and nuts; fruit
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Granivore ); omnivore
Spermophilus beecheyi is found throughout most of California, most of Western Oregon and portions of Western Nevada. This species also occurs in portions of southwestern Washington, and Baja California.
Biogeographic Regions: nearctic (Native )
Spermophilus beecheyi has successfully exploited many habitat types. California ground squirrels are terrestrial, and semifossorial, requiring habitats with some loose soil where they can excavate an appropriate burrow.
You may find them colonizing fields, pastures, grasslands and in open areas such as oak woodlands. The only habitat they do not use is deserts. You may find them down in valleys and up on rocky outcrops in the mountains, to an elevation of 2,200 m. They can be found in urban, suburban and agricultural areas. By and large this species is widely distributed within its range.
Range elevation: 0 to 2200 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: chaparral ; mountains
Other Habitat Features: urban ; suburban ; agricultural
The lifespan of a California ground squirrel can be up to 6 years in the wild. They have lived as long as 10 years in captivity.
Range lifespan
Status: wild: 6 (high) years.
Range lifespan
Status: captivity: 10 (high) years.
California ground squirrels have mottled fur, with gray, light and dark brown, and white present in their pelage. They typically have a darker mantle. The shoulders, neck and sides of this species are a lighter gray. The bushy tail is a combination of the colors that appear on the back. The underside is a lighter combination of light brown, gray and white. California ground squirrels have a white ring around each eye.
The body length can range from 330 to 508 mm and tail length from 127-229 mm. These animals range in weight from 280 to 738 g. The ears are > 10 mm and < 25.4 mm. The dental formula is 1/1 : 0/0 : 2/1 : 3/3 = 22.
Range mass: 280 to 738 g.
Range length: 330 to 508 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
These ground squirrels are highly vulnerable to predation due to their diurnal habits, open habitat, and the concentrations of conspecifics found in any particular colony. They are known to be preyed upon by red-tailed hawks, golden eagles, coyotes, foxes, badgers, weasels, house cats, dogs, and wild cats such as bobcats and pumas. In addition, large snakes may prey upon them.
Spermophilus beecheyi individuals probably avoid predation mainly through the use of burrow systems and vigilance. They are also cryptically colored. Also, they have skin glands on their back, just posterior to the shoulders, which secrete an odorous oil which could deter predators.
Known Predators:
Anti-predator Adaptations: cryptic
Females of this species are considered promiscuous. They will often mate with more than one male, either through force or selectivity, and therefore the offspring of a single litter may have multiple paternity. Males may also mate with several females.
Mating System: polygynandrous (promiscuous)
The mating season of S. beecheyi occurs in early spring, typically for a few weeks only. As with most ground-dwelling squirrels, breeding occurs just after the animals emerge from their winter burrows. This is highly dependent on the area and climate the squirrel inhabits, since the timing of hibernation varies geographically, with elevation, and with other ecological factors.
Males possess abdominal testes which drop into a temporary scrotum during the breeding season only.
Females produce one litter per year after of a gestation period of roughly one month. Litters range in size from five to eleven young. The sex ratio of young are about 1:1.
Young S. beecheyi may open their eyes at around 5 weeks of age. They first leave burrows at 5 to 8 weeks of age, and are wenaed between 6 and 8 weeks. The coloring of the young is somewhat lighter than that of adults. Molting for young begins a few weeks after they emerge from their burrows. Young may begin to burrow at 8 weeks of age. They reach sexual maturity no sooner than 1 year old. In the first year of life, some ground squirrels remain above ground and do not hibernate.
Breeding season: Breeding begins shortly after emergence from hibernation. Timing of the breeding seasons varies, depending upon when the animals end their hibernation.
Range number of offspring: 5 to 11.
Average gestation period: 1 months.
Range weaning age: 6 to 8 weeks.
Range age at sexual or reproductive maturity (female): 1 (low) years.
Range age at sexual or reproductive maturity (male): 1 (low) years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
The only active parenting is provided by the mother. Females give birth to their pups in a burrow, and will move young into new burrows frequently to avoid predation. Young are helpless at birth, and their eyes do not open until they are about 5 weeks old. Shortly after their eyes open, the young pups leave the burrow and begin to explore their surroundings.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The California ground squirrel (Otospermophilus beecheyi), also known as the Beechey ground squirrel,[4] is a common and easily observed ground squirrel of the western United States and the Baja California Peninsula; it is common in Oregon and California and its range has relatively recently extended into Washington and northwestern Nevada. Formerly placed in Spermophilus, as Spermophilus beecheyi, it was reclassified in Otospermophilus in 2009, as it became clear that Spermophilus as previously defined was not a natural (monophyletic) group.[5] A full species account was published for this species in 2016.[6]
John Richardson, who originally described the species as Arctomys (Spermophilus) beecheyi, or "Beechey's marmot", named it after Frederick William Beechey, an early 19th-century British explorer and naval officer.[3]
The squirrel's upper parts are mottled, with the fur containing a mixture of gray, light brown and dusky hairs. The shoulders, neck and sides are a lighter gray. The fur around the eyes is whitish. The underside is lighter, buff or grayish yellow. Head and body are about 30 cm (12 in) long and the tail an additional 15 centimetres (5.9 in). They can weigh from 280 to 738 g (9.9 to 26.0 oz).[7] The tail is relatively bushy for a ground squirrel, and at a quick glance, the squirrel might be mistaken for a fox squirrel.[8]
As is typical for ground squirrels, California ground squirrels live in burrows, which they excavate themselves. Some burrows are occupied communally, but each squirrel has its own entrance.[8] Although they readily become tame in areas used by humans, and quickly learn to take food left or offered by picnickers, they spend most of their time within 25 m (80 ft) of their burrows, and rarely go further than 50 m (160 ft) from it.[8]
In the colder parts of their range, California ground squirrels hibernate for several months, but in areas where winters have no snow, most squirrels are active year-round. In those parts where the summers are hot, they may also estivate for periods of a few days.[9]
California ground squirrels are often regarded as pests in gardens and parks, since they eat ornamental plants and trees. They commonly feed on seeds, such as oats, but also eat insects such as crickets and grasshoppers, as well as various fruits.[10] The dental formula of O. beecheyi is 1.0.2.31.0.1.3 × 2 = 22.[11]
California ground squirrels' mating season is early spring and tends to last only for a few weeks. The females are considered to be promiscuous, so the individuals of one litter can be from multiple mates. The California ground squirrel has one litter of five to eleven per year, with gestation around one month. The young open their eyes at about five weeks and reach sexual maturity around one year old.
The coloration of the young is slightly lighter than the adults, and molting occurs at about eight weeks of age – when the young leave the burrows.[12] California ground squirrels can live up to six years.[7]
California ground squirrels use their cheek pouches to store more food than can be consumed in one sitting to store it for a later date. They are considered to be mostly herbivorous, with seeds, grains, nuts, fruits, and sometimes roots constituting most of their diet.[12]
California ground squirrels are frequently preyed on by rattlesnakes. They are also preyed on by eagles, raccoons, foxes, badgers, and weasels. Interdisciplinary research at the University of California, Davis, since the 1970s has shown that the squirrels use a variety of techniques to reduce rattlesnake predation. Some populations have varying levels of resistance to rattlesnake venom as adults. Female squirrels with pups also chew on the skins shed by rattlesnakes and then lick themselves and their pups (that are never resistant to venom before one month of age) to disguise their scent.[13] Sand-kicking and other forms of harassment provoke the snake to rattle its tail, which allows a squirrel to assess the size and activity level (dependent on blood temperature) of the snake.[14]
Another strategy is for a squirrel to super-heat and swish around its tail.[15] When hunting, rattlesnakes primarily rely on their pit organ, which detects infrared radiation. The hot tail-swishing appears to convey the message "I am not a threat, but I am too big and swift-moving for it to be worth trying to hunt me." These two confrontational techniques also distract the snake from any nearby squirrel burrows containing pups.
The swishing of the tail from side to side is called tail-waving, which helps the squirrel to deter a snake attack. The snakes attacked the squirrels that exhibited the tail-waving at a shorter distance than those that did not and majority of those tail-waving squirrels successfully dodged these attacks. This successful dodging, along with the fact that the adult squirrels are larger than the young ones, helps to deter the predators, as the rattlesnakes are 1.6 times more likely to be deterred from attacking an area after an encounter with an adult squirrel. In 30 out of 45 interactions with snakes, the tail-waving behavior of the squirrels stopped the snake in its tracks and the snake attempted to wait for the squirrel to leave before it would consider attacking again, showing that the behavior does deter predatory attacks by the rattlesnakes.[16] This is due to the adult squirrels being vigilant and looking more threatening and also that they are able to more successfully dodge attacks. They also can use their tail-waving to signal to other ground squirrels in the area that a rattlesnake or other predator has recently been spotted. Though the ground squirrels have been found to also exhibit this tail-waving behavior when no predator is present, they wave their tails faster and for a longer time when they spot a predator or in an area where a predator has recently been spotted.[17]
Vigilant behavior in squirrels is also a defense mechanism to avoid predation. In addition to the tail-waving, the squirrels have been found to be more vigilant and on alert if a predator had recently been in the area than they were if no predator had been detected.[17] If the ground squirrels are aware that they are in an area where the rattlesnakes have recently been, they devote more time to being alert and searching for the predators than to hunting and foraging than in an environment where they do not believe predators exist.[10] These vigilant squirrels were found to have a faster reaction time to a stimulus from a predator and jump higher and further away than a squirrel that was not as vigilant. In a simulated environment study, 60% of squirrels that were in an environment with a recent snake encounter exhibited an evasive leap behavior, which propels them farther away from their attackers; 20% of squirrels exhibited this behavior in a primary encounter with a snake and roughly 5% of squirrels exhibited this behavior when no snake was present and no threat was detected. This shows that the squirrels are more alert, vigilant, and ready for an attacker after one has been recently seen.[17]
The California ground squirrel (Otospermophilus beecheyi), also known as the Beechey ground squirrel, is a common and easily observed ground squirrel of the western United States and the Baja California Peninsula; it is common in Oregon and California and its range has relatively recently extended into Washington and northwestern Nevada. Formerly placed in Spermophilus, as Spermophilus beecheyi, it was reclassified in Otospermophilus in 2009, as it became clear that Spermophilus as previously defined was not a natural (monophyletic) group. A full species account was published for this species in 2016.
